The quest for technically feasible and economic techniques for converting coal to suitable liquid fuelds has continued for more than 100 years. Recent political and economic developments have impelled accelerated research in this field.
The soaring price of crude oil has induced increased research on coal liquifaction and gasification. As illustrated by U.S. Pat. Nos. 3,607,718, 3,652,446, 3,870,621 and 4,054,504, it has been suggested that liquified coal can be upgraded into useful fuels by fluid catalytic cracking and hydro-cracking processes. Riser cracking of coal liquifaction liquids has been suggested in U.S. Pat. Nos. 4,081,351 and 4,108,758.
The available riser cracking processes generally involve careful pretreatment of the coal, such as for instance by completely dissolving the coal and separating out undesirable components, prior to introducing the coal into the cracking zone. Moreover, it has been suggested to hydrogenate the coal upstream of the riser, i.e. during the solubilization process. The present invention is aimed at providing a process in which at least a portion of the hydrogenation of the coal can be accomplished in the riser itself, while making use of catalysts bearing metals accumulations generally regarded as harmful in the past.